Method and apparatus for casting



De@ 1, l942- w. c. BROWN 2,303,679,

METHOD AND APPARATUS FOR CASTING y Dec' 1, 194.12- 1 w. c. BROWN A.2303;679

METHOD AND APPARATUS FOR. CASTING Filed Jun 13,l 1940 2 Sheets-Sheet 2.Wneg 5.46. 7%?,10

Patented Dec. l., 1942 UNITED .STATES PATEN? FFICE 9 Claims.

The present invention relates to electrical equipment and methods andapparatus for assembling the same, and is more particularly concernedwith the formation of electrical connections in complicated assemblies,such as radio receivers.

According to usual methods of manufacturing radio receivers the largerparts, such as audiofrequency transformers, intermediate-frequencycoils, variable condensers, tube sockets and the like, are mounted on achassis. The necessary electrical connections are then made by solderingwires to suitable lugs on these parts. This method of assembly is notonly expensive but, since it is done by hand under high-speedconditions, frequently gives rise to poor joints and misplacedconnections. Furthermore, due to the random placing of the connections,stray capacitances and mutual induct'ances will vary from set to set,thus requiring nal adjustments in an effort to obtain uniformity ofperformance.

The object of the present invention is primarily to avoid thedisadvantages above noted, with a view to reducing the cost ofmanufacture and improving the uniformity of performance and operation.

With this and other objects in View as will hereinafter appear, thepresent invention comprises electrical equipment and the method andapparatus for its assembly hereinafter described and particularlydefined in the claims.

In accompanying drawings Fig. 1 is a simplified isometric view of achassis of a radio receiver in which the wiring assembly is to be formedaccording to the present invention; Fig. 2 is a view of the solder bath;Fig. 3 is a view of the chassis with the Wiring assembly completed; Fig.4 is a View of the mold base and associated parts; Fig. 5 is a detailView of la jig for bending connections; Figs. 6, 7 and 8 are detailviews illustrating the formation of wiring connections at two levels;and Figs. 9 to 12 are detail views illustrating a modified and preferredmethod of forming Wiring connections at two levels.

The invention will now be specifically described as embodied in a methodand 'apparatus for forming certain electrical connections between partsof a radio receiver. In Fig. 1 there is illustrated a chassis I on whichare mounted two tube sockets l2 and i4, each with downwardly extendinglugs l to which electrical connections are to be made. It will beunderstood that the usual chassis base will also include other pieces ofequipment, such as audioand intermediatefrequency transformers as wellas a greater number of tube sockets, all such equipment havingconnecting lugs similar to the lug i6. The principles of the inventionare, however, applicable to any wiring assembly regardless of itscomplexity, and for reasons of convenience it will be assumed that inthis specific instance connections are to be established only betweenthe lugs of tube sockets I2 and lli, together with the introduction ofcertain small component parts which are to be presently described.

In Fig. 3 is shown the assembly as it appears when completed (thechassis being here inverted with respect to Fig. 1). The assemblyinvolves various connections between the lugs of the tube sockets, aswell as the connection and support of two small component parts i8 and20. In general, these component parts comprise small elements such asresistors and fixed condensers which do not need to be mounted on thechassis and are supported in the finished assembly by the connectionsthemselves. yIhese parts are here shown as fixed resistors.

The connections are formed by immersing the lugs i6 into a soldering pot22 (Fig. 2), in which la mold base is also immersed. The mold base 24,as shown in Fig. 4, comprises a plate formed with openings 26 to permitdrainage of molten solder. Mounted on the base are a number of moldingtroughs indicated at 28, 3l), 32, 34 and 36 of such lengths andconfigurations as to provide the desired wiring layout for the assembly.Preferably each mold comprises a piece of stock of the proper shape fromwhich a trough has been milled or otherwise formed in its uppe surface.

Also mounted on the mold base 24 are two supporting pans 3B and 40 tohold the parts I8 and 2li during the molding operation. Each pancomprises a piece of stock suitably hollowed in its upper surface toform an accurate positioning means for the part which is to be retained.

The several trough molds and supporting pans, as well as the base 24,are constructed of stock, preferably aluminum, which is not wet by thesolder alloy, so that upon removal of the entire mold from the solderpot, the solder will run off without sticking to any of these parts. Thetrough molds 28 to 35 are of such a height that they are submerged inthe bath and the supports 38 are il are of sufficient height to extendslightly vabove the level of the bath.

Prior to immersion of the mold, the resistors It and 20 are placed inthe pans 38 and fill. The leads at the ends of the resistors may be bentin a preceding operation so that their ends will properly enter thedesired molding trough, as is illustrated for the part IB. 0r,alternatively, the leads may be initially straight, subject to a bendingoperation after the resistor is mounted in the supporting pan. Thislatter procedure is illustrated for the resistor 20. After placing theresistor 20 in the pan 40, a bending jig 42, shown in Fig. 5, is broughtdown over the mold assembly in proper register therewith. The jig isprovided with downwardly extending notched plates 44 which arepositioned to engage the protruding leads and bend them downwardly intotheir respective molding troughs. As shown in Fig. 4 the leads at theend of the resistor 20 have been thus bent down by the action of thebending jig.

The chassis l0 is then registered with the mold base, and the entiremold is immersed in the solder pot. Rods 43 at the corners of the moldbase serve not only to register the c parts, but also as convenientgrips to assist in lowering the mold and chassis into the solder DOt. Ifdesired, the mold base may be immersed rst and the chassis mayafterwards be placed over it. In either case the troughs (28 to 36) arecompletely submerged while the resistors I8 and 20 are supported out ofthe bath. Preferably the parts are so arranged that the ends of thechassis abut the rods 48, and the aprons 49 of the chassis fit over thesides of the solder pot.

It has been found in some instances that the solder does not ow readilyinto the molding troughs on immersion, but the flow maybe enhanced byimparting a vibration to the mold,

preferably by applying a vibrating hammer of any suitable type to one ofthe rods 48. Alternatively, the lling of the troughs may be accomplishedby removing and re-submerging the mold once or twice, with or Withoutsome vibration, but the method of relying on vigorous vibration only isconsidered preferable because it is more rapid and affords less time fordamage to the resistors due to heating. As soon as the troughs arefilled, the chassis base and the mold assembly are lifted bodily fromthe bath by the rods 48. The excess solder runs back into the baththrough the holes 26 and only the proper amount of solder remains in thetroughs to form the desired connections. vibration is continued duringthe removal of the mold from the bath, in order to insure proper ow ofthe solder around the various connections.

The parts are then subjected to forced cooling, conveniently by a fan,not only for the purpose of rapidly hardening the solder but also toprevent overheating of the resistors I8 and 2l). The chassis base canthen be easily freed from the mold since the solder does not stick tothe aluminum mold parts. With molding troughs of the shape ,shown inFig. 4 the connections illustrated in Fig. 3 will be formed.

It will be understood that the connections of Fig. 3 are illustrativeonly, and that connections may be formed according to any desiredarrangement.

In electrical apparatus of considerable complexity it is frequentlynecessary to form the connections in two or more levels because of themultitude of Crossovers and the space requirements for parts. It willbel understood that it is impossible in a single level to form solderconnections which are to cross one another Without electrical contact.For such complex as- Preferably the semblies, of which radio receiversmay be taken as an example, the present invention provides for makingconnections at tWo levels. For this purpose two alternative proceduresmay be fol lowed.

In Fig. 6, I have illustrated a tube socket 5U which is provided withspecial lugs 52, each of a type to permit multiple electricalconnections at different levels. Each lug 52 comprises a connector 54 ofthe same length as one of the standard single lugs i6 of the socketpreviously described, and a longer connector 56, these parts beingattached together by a web 58. For the connections at the first levelthe part 54 is introduced into its molding trough (indication at 68)exactly as heretofore described. After the formation of the first levelconnections, typified by the hardened solder bar 62, the Whole assemblyis immersed in another solder bath in which a different mold assemblyhas been submerged. This second mold assembly is similar to thatpreviously described except for the different layout of connections, themolding troughs 64 thereof (Fig. 8) being designed to register with thelong connectors 56. As shown in Fig. 8 where considerations of space areimportant, as in the case of tube sockets, the connector 56 may bemanually bent so that its end lies under the end of the connector 54prior to introduction into the second level mold assembly.

It will be understood that certain electrical connections will be formedat one level only, for which purpose single connectors of the properlengths may be used.

Another and preferred method of making multiple connections in more thanone layer is shown in Figs. 9 to 12. As here shown the lugs used formultiple connections are of simple wire form but long enough to extendthrough both levels, as indicated at SE. For the first level molding, atrough 68 is used, having an opening through which the lug B6 passes.After the molding of the first level and the withdrawal of the mold andchassis from the bath, a certain amount of solder A will cling to thebottom ends of the long lugs as indicated at 10 in Fig. 10. These endsare heated for the purpose of melting the solder which clings thereto.This heating is most easily carried out by re-immersion of such ends insolder, as indicated diagrammatically in Fig. 11, to only such depth andfor such time as required to melt off the solder 'lil without affectingthe previously formed solder joints. The lugs 66 can then be Withdrawnthrough the holes in the molding i troughs 68 before any of the soldermaterial has an opportunity to harden thereon. Thus the rst level ofconnections is completed. The second level of connections is then formedby introducing the bottom ends of the lugs 6B into submerged moldingtroughs 1'2 which have been shaped in accordance with the desired secondlevel layout (Fig. 12). This process may be repeated for any munber oflevels but it has been found that in electrical equipment typified byradio receivers the formation of two levels of connections is generallysuicient.

It will be understood that although a radio receiver has been taken asan example, the invention is equally applicable to electrical equipmentof other types, and further, that although simplified connections areherein shown, the invention is applicable to assemblies of any degree ofcomplexity. In other respects, also, the invention is not to beconsidered as limited to the precise embodiment herein described. Forexample, the

term chassis" as herein used is meant to apply to a panel or base onwhich equipment is mounted, and the term solder applies to any moltenmaterial which is capable of hardening upon cooling to form theconnections determined by the arrangement of the mold troughs.

Having thus described the invention, I claim:

l. A method of assembling and forming electrical connections for complexelectrical apparatus which consists in taking a chassis having lugsthereon, immersing the lugs in register with mold troughs in a solderbath, said troughs being of a size to form long and narrow connections,supporting a component part out of contact with the solder, thecomponent part having leads extending into mold troughs, removing themold and chassis together from the bath, and separating the chassis withits formed connections from the mold after hardening of the solder.

2. A method of assembling and forming electrical connections for complexelectrical apparatus which consists in taking a chassis having lugsthereon, immersing the lugs in register with mold troughs in a solderbath, said troughs being of a size to form long and narrow connections,said immersion being repeated to insure ilow of solder into the troughs,removing the mold and chassis together from the bath, and separating thechassis with its formed connections from the mold after hardening of thesolder.

3. A method of assembling and forming electrica1 connections for complexelectrical apparatus which consists in taking a chassis having lugsthereon, immersing the lugs in register with mold troughs in a solderbath, said troughs being of a size to form long and narrow connections,removing the mold and chassis together from the bath, separating thechassis from the mold, immersing the lugs in a bath in conjunction withanother mold to form connections at another level, removing the chassisand second mold from the bath, and separating the chassis from thesecond mold.

4. Apparatus for assembling and forming electrical connections forelectrical equipment comprising a mold base having long and narrowtroughs thereon, a solder pot to contain a bath in which the mold baseis immersed, supports on the base to hold component parts out of contactwith the solder, means for immersing soldering lugs on a chassis inregister with the troughs, and means for removing the mold base andchassis together from the bath.

5. Apparatus for assembling and forming electrical connections forelectrical equipment comprising a mold base having long and narrowtroughs thereon, a solder pot rto contain a bath in which the mold baseis immersed, supports on the base to hold component parts out of contactwith the solder, certain of the troughs being arranged to receive leadsconnected'with said component parts, means for immersing soldering lugson a chassis in register with the troughs, and means for removing themold base and chassis together from the bath.

6. In apparatus for assembling and forming electrical connectionsfor-electrica1 equipment, a solder bath, a plurality of molds havinglong and narrow troughs to form connections at different levels, andmeans for registering connectors on pieces of electrical equipment withthe troughs of each of the molds successively.

7. In apparatus for assembling and forming electrica1 connections forelectrical equipment, said equipment having Jugs with multipleconnectors to form connections in different sets, a mold having troughsto register with one set of connectors, a second mold having troughs toregister with another set of connectors, and solder bath means in whichthe lugs are immersed in successive register with the molds.

8. In apparatus for assembling and forming electrical connections forelectrical equipment, a mold having long and narrow troughs to registerwith connectors on said equipment, including troughs having openings topermit passage of long connectors therethrough, a second mold havingtroughs to form connections at a diierent level and including troughsregistering with the ends of said long connectors, and solder bath meansin which the molds and the connectors are immersed.

9. A method of assembling and forming electrical connections forelectrical equipment which consists in taking achassis havingconnectors, immersing in a solder bath a mold to form electricalconnections to said connectors, immersing the connectors in the bath inregister with the mold and with connectors passing through the mold,removing the mold and chassis from the bath, heating the ends of theconnectors to free them of the mold, and repeating the molding operationwith a different mold to establish connections at the ends of theconnectors.

WILLIAM C. BROWN.

